WIP - feat(ways): plugin way discovery (ADR-129)

[ctracey]

Summary

Extends the way discovery system to scan enabled Claude Code plugins for ways, enabling plugin authors to ship domain-specific guidance alongside their tools.

• Hybrid discovery: Session-start hook resolves plugin paths once via claude plugin list --json, writes a session manifest; per-invocation scans read from the manifest
• Three-tier precedence: project-local > plugin > global (existing ways always win)
• ID namespacing: Plugin ways prefixed as plugin:{plugin_id}/{way_path} to prevent collisions
• Corpus integration: ways corpus discovers plugin ways outside sessions via installed_plugins.json
• Macro trust: Plugin macros execute without trust prompts (plugins are already user-approved)
• Scope filtering: Project-scoped plugins only surface their ways when the active project matches

Architecture

Design documented in ADR-129. Key decisions:

1. Session manifest over per-scan CLI calls — claude plugin list is too slow to run on every hook invocation; resolving once at session start amortizes the cost
2. Fallback chain — File resolution tries installed_plugins.json first (fast, no session context needed), then falls back to session manifest
3. No version dedup — Plugin registry already ensures one enabled version per ID; we trust the registry rather than reimplementing version logic

Changes

Area	Files	What
Hook	hooks/ways/resolve-plugins.sh	Session-start hook that queries plugin CLI, writes manifest
Config	settings.json	Registers the new hook in SessionStart chain
Discovery	src/cmd/scan/candidates.rs	collect_plugin_candidates(), prefixed dir scanning
Resolution	src/session.rs	plugin_way_dirs(), resolve_way_file_in_session(), fallback chain
Show	src/cmd/show/mod.rs	Session-aware file resolution for ways and checks
Corpus	src/cmd/corpus.rs	Plugin way discovery for offline corpus builds
ADR	docs/architecture/system/ADR-129-*	Design document

Test plan

9 scenarios covering the plugin discovery surface, documented in SIMULATION-SPEC.md §9:

• 9a — Plugin way appears in scan candidates with plugin: prefix
• 9b — Plugin way fires through show::way pipeline (markers stamped)
• 9c — Multiple plugins merge into unified candidate list
• 9d — Project-local way with same ID shadows plugin way
• 9e — Project-scoped plugin excluded from non-matching project
• 9f — Plugin check fires and pulls parent way
• 9g — Missing/empty manifest degrades gracefully (zero candidates)
• 9h — Plugin macro executes without trust gate
• 9i — Disabled plugin excluded from manifest

All 19 tests pass (9 new + 10 existing, zero regressions):

test scenario_11a_plugin_way_in_scan ... ok
test scenario_11b_plugin_way_fires ... ok
test scenario_11c_multi_plugin_merge ... ok
test scenario_11d_project_shadows_plugin ... ok
test scenario_11e_project_scope_filter ... ok
test scenario_11f_plugin_check_fires ... ok
test scenario_11g_missing_manifest ... ok
test scenario_11h_plugin_macro_runs ... ok
test scenario_11i_disabled_plugin_excluded ... ok

[ctracey]

TODO

• complete manual user review
• add docs regarding plugin support
• make sure ways rethink is working with plugins